Starter for low voltage fluorescent lamps



F. KNOBEL I 3,333,075

STARTER FOR LOW VOLTAGE FLUORESCENT LAMPS July 25, 1967 Filed Dec. 27, 1965 Fig. 1

Fig 4 INVENTOR FRITZ KNOBEL United States Patent Filed Dec. 27, 1965, Ser. No. 516,570 Claims priority, application Switzerland, Jan. 15, 1965, 558/65 11 Claims. (Cl. 200-1135) The present invention pertains to starters for low voltage fluorescent lamps of the kind having a tapped choke or ballast and a normally closed switch operated by the expansion and contraction of a hot wire.

Under certain conditions, such as worn-out fluorescent lamps, defective lamps, extremely low ambient temperatures, very low voltage in the power supply system or in the lamp circuit, it occurs that starters of this kind over a prolonged period continue to attempt to start the lamp.

When the condition continues for some time, because the lamp fixture is not readily accessible, for example, the contacts and other essential components of the lamp circuit .are overloaded, preventing reliable performance. Such operation of the starter also causes radio interference, which is preferably avoided.

The prior art discloses starters which, to prevent continued operation of the starter, have a flicker suppressor, wherein the heating of the contacts or the interrupted curcent flow in the starter circuit serves to open the starter circuit or to permanently open the starter contacts after a certain lapse of time. With these known devices it is essential after operation of the flicker suppressor or of the excess current cut out that they be reset by hand at the lamp. Provision of manual reset must be allowed for when the starter -or the excess curent cutout is designed for incorporation into the lamp fixture. These conditions are only met difilcultly at the price of increased complication and higher cost. In instances where the flickering is only temporary, such as occur with street lights at very low temperatures or with low voltages in the power supply system, it obviously is not desirable to have to reset the flicker suppressor. This is undoubtedly one reason why known starters with suppressors have not found acceptance.

An object of the invention is a starter having a flicker suppressor which prevents continued operation of the starter when the lamp will not start and which is automatically reset when the lamp circuit is switched off.

This and other objects of the invention will be apparent from the following detailed description, and from the drawings, wherein:

FIGURE 1 shows the starter before operation;

FIGURE 2 shows the starter after a lamp has correctly started;

FIGURE 3 shows the starter after operation of the flicker suppressor;

FIGURE 4 is a simplified schematic diagram of a starter circuit with the lamp cathodes series connected to the current source; and

FIGURE 5 is a simplified starter circuit with the lamp cathodes'connected so that, without a suppressor, they would be repeatedly heated should the lamp not start.

Referring to FIGURE 1, a housing 1 of electrically insulating material has mounted within it the stationary and movable contacts 2, 3 of a normally closed switch 3A together with their respective connecting lugs 4, 5. Also mounted inside the housing is a generally U-shaped bar 6 connected to a lug 7. A lug 8 is connected, via a loop of resistance wire 9, to a pin 10 rigidly connected to the bar 6 and insulated therefrom. The loop limits the current drawn. The lug 8 can also be connected to the pin 10 via 3,333,075 Patented July 25, 1967 "ice ' a conductor having a negative temperature coefficient rather than the resistance loop.

A sleeve 11 is mounted for rotation on the pin 10. One end of a hot wire 12 is wound around the sleeve and the other end is made fast to the bar *6. The hot wire 12 is thus electrically connected to the lugs 7, 8. A control lever 13 is rigidly connected to the sleeve 11. The end of the lever acts on a contact 14 that is mounted on and insulated from the movable contact 3. By means of a copper conductor 15 connected between the contact 14 and the lug 8, the loop of resistance wire 9 is shorted out when the contact 3 is open. The current path between lugs 7, 8 is now along wire 12, sleeve 11, lever 13, contact 14, and conductor 15. A tension spring 16 pulling upon the arm 13 keeps the hot wire 12 under tension.

A bimetallic contact 18 is mounted on the movable contact 3 and in electrical connection therewith by means of a rivet 17, such that when the rivet is heated the heat is conducted to the bimetallic contact 18, which is caused to bend towards an opposing contact 19. Upon suflicient bending the separation, which is determined by a stop 20, between the bimetallic contact 18 and the contact 19 is bridged. The contact 19 is connected to a lug 24 via a heating filament 21, a bent arm 22 mounted on the housing 1 and insulated therefrom, and a mounting screw 23. The filament 21 is located adjacent the bimetallic contact, for heating the latter.

FIGURE 2 shows the starter as it appears in normal operation: that is, after the fluorescent lamp has correctly started, without previous flickering, and the starter contacts 2, 17 are held apart, in consequence of the operating current heating the hot wire 12, which sufficiently lengthens to permit the arm 13, under action of the tension spring 16, to pivot downwards,.-press on the contact '14, and force contact 3 to move away from contact 2. Inasmuch as the bimetalic contacts 18 are thus not heated,

.. does not start, causing wire 12 to cool, and the contacts 2, 3to close. The repetition of this sequence, and the large starting current that repeatedly flow through the contacts 2, 3, cause contact 17 and thus the bimetallic contact 18 to heat, which latter bends and touches the opposing contact 19.'Consequently, a current flows via these contacts through the heating filament 21, the bent arm 22, and the screw 23 to the lug 24, which is corinected to the lug 4, thus jumping the switch 3A, which remains continuously open because current now can flowthrough the wire 12. A current continuously flows through the heating filament, keeping the bimetallic contact 18 hot and :bent, until the lamp is shut off, whereupon the.

bimetallic contact cools andreturns to its original position. The cooling and contraction of the hot wire 12 causes the lever 13 to pivot upwardly, thereby permitting the movable contact 3 to return to its position of contact with contact 2. Because every time the lamp is switched off all parts of the starter return to their original positions, the starter operates in the normal manner when the lamp is again turned on. The value of the current flowing in the circuit under the conditions of FIGURE 3 corresponds to the preheating current of the lamp cathodes.

If the start winding of the ballast or the provision of a series-connected capacitor assures that the said value of the current is not suflicient to overheat the ballast, the

automatically acting flicker suppressor of the invention prevents damage to any of the components of the lamp circuit.

In order to prevent the coming together of contacts 18, 19 caused by high ambient temperatures and to ensure that very low temperatures will not prevent a sufficient bending of the bimetallic contact so that it can touch contact 19, the latter is carried by a bent bimetallic arm 25, such that the bimetallic contact 18 and arm 25 are relatively so designed that the separation between contacts 18, 19, as seen in FIGURE 2, remains virtually constant through an ambient temperature range of -20 C. to +100 C. (approximately 4 F. to +212 F.).

Referring .to the circuit diagram of FIGURE 4, the lugs 7, 8 are connected to starting taps of a choke or ballast 26. The cathodes 27, 28 of the fluorescent lamp 29 are connected to the lugs 4, and in series with the choke 26. A capacitor 30, serving to facilitate starting and to suppress radio interference, is connected in parallel with the lamp. Terminals 31, 32 are connected to a source of voltage.

The circuit diagram of FIGURE 5 differs from that of FIGURE 4 in that the cathodes 27, 28 are connected across portions of respective windings of a choke 26. With this circuit the starter circuit through contacts 2, 3 is not opened when the lamp 29 is removed from its fixture or when one or both cathodes 27, 28 are defective. The starter continues to function when the fixture no longer contains a lamp, so that the use of a starter having automatic flicker suppression, as shown in the schematic diagram, is particularly important in this instance.

- The circuits of both figures can have series or parallel connected capacitors for the purpose of phase correction. Series connection has the advantage that the sustained short-circuit current after operation of the flicker suppressor is limited to a value approximately that of the normal current.

I claim:

1. Starter with flicker suppressor for low voltage fluorcscent lamps: a normally closed switch having first and second contacts for completing the starting circuit for the lamps, said first contact :being connected to one side of the starting circuit and said second contact being connected to the other side of the starting circuit; temperature responsive means connected to carry at least a portion of the current flowing through said starting circuit, said means expanding when heated by the current flowing through it and the expansion thereof causing said switch to open; a third contact movable independently of said second contact and in electrical and thermal connection therewith, the position of said third contact being determined by its temperature in dependence on an abnormal rise in the temperature of said second contact with respect to the ambient temperature, caused by repeated operation of the starter; a fourth contact spaced from said third contact, said third contact being brought into electrical contact with said fourth contact under the influence of said abnormal temperature rise and returning to its original position when the temperature rise no longer exists; electrical conductor means connecting said fourth contact to said one side of the starting circuit; whereby when said third and fourth contacts are in electrical connection said switch is jumped permitting the continued flow of current through said temperature responsive means, thus holding said switch open and preventing the continued repeated operation of the starter,

2. The starter of claim 1, including electrical heating means connected in series with said third and fourth contacts, for heating said third contact to keep the latter in contact with said fourth contact until the lamp is shut off.

3. The starter of claim 1 including means for maintaining the separation between said third and fourth contacts approximately constant over a wide range of ambient temperatures.

4. The starter of claim 1, including bimetallic means that determines the position of said third contact.

5. The starter of claim 1, including bimetallic means supporting said fourth contact.

6. The starter of claim 3, wherein said means comprises individual bimetallic support means for said third and fourth contacts.

7. The starter of claim 1, including a ballast, means electrically connecting said temperature responsive means across a portion of the ballast winding, and means for electrically connecting the cathodes of a fluorescent lamp in series with the winding of said ballast.

8. The starter of claim 1, including a ballast having two windings, means electrically connecting said temperature responsive means across a portion of one of the ballast windings, and means for electrically connecting each cathode of a fluorescent lamp across a portion of a respective winding.

9. The starter of claim 1, including a ballast, a separate start winding of said ballast connected to said temperature responsive means, for limiting the current drawn when said third and fourth contacts are in electrical connection.

10. The starter of claim 1, wherein said temperature responsive means is a hot wire, and including pivotally mounted lever means for movement to a position to open said starter, said hot wire being connected to said lever means for movement of the latter by expansion of the hot wire to said position.

11. An automatic switch for the ignition and operation of a fluorescent lamp, said switch including a pair of terminals and a pair of normally closed contacts adapted to pass electrical current between said terminals for lamp ignition purposes and constituting a first heating means,

time delay means responsive to current flow between said terminals through said normally closed contacts to open said normally closed contacts after a predetermined period of time,

a normally open temperature responsive switch associated with said first heating means and adapted to be closed thereby only in response to repetitious operation of said first heating means as occasioned by repeated failure of the associated lamp to ignite,

and second heating means actuated in response to closing of said temperature responsive switch for maintaining said temperature responsive switch in closed condition.

References Cited UNITED STATES PATENTS 2,302,285 11/ 1942 Aggers 200-122 2,491,858 12/1949 Hehenkamp et al. 200-122 2,936,403 5/ 1960 Knobel ZOO-113.5 3,166,655 12/1965 Kline 200-113 BERNARD A. GILHEANY, Primary Examiner. H. E. SPRINGBORN, Assistant Examiner. 

1. STARTER WITH FLICKER SUPPRESSOR FOR LOW VOLTAGE FLUORESCENT LAMPS: A NORMALLY CLOSED SWITCH HAVING FIRST AND SECOND CONTACTS FOR COMPLETING THE STARTIONG CIRCUIT FOR THE LAMPS, SAID FIRST CONTACT BEING CONNECTED TO ONE SIDE OF THE STARTING CIRCUIT AND SAID SECOND CONTACT BEING CONNECTED TO THE OTHER SIDE OF THE STARTING CIRCUIT; TEMPERATURE RESPONSIVE MEANS CONNECTED TO CARRY AT LEAST A PORTION OF THE CURRENT FLOWING THROUGH SAID STARTING CIRCUIT, SAID MEANS EXPANDING WHEN HEATED BY THE CURRENT FLOWING THROUGH IT AND THE EXPANSION THEREOF CAUSING SAID SWITCH TO OPEN; A THIRD CONTACT MOVABLE INDEPENDENTLY OF SAID SECOND CONTACT AND IN ELECTRICAL AND THERMAL CONNECTION THEREWITH, THE POSITION OF SAID THIRD CONTACT BEING DETERMINED BY ITS TEMPERATURE IN DEPENDENCE ON AN ABNORMAL RISE IN THE TEMPERATURE OF SAID SECOND CONTACT WITH RESPECT TO THE AMBIENT TEMPERATURE, CAUSED BY REPEATED OPERATION OF THE STARTER; A FOURTH CONTACT SPACED FROM SAID THIRD CONTACT, SAID THIRD CONTACT BEING BROUGHT INTO ELECTRICAL CONTACT WITH SAID FOURTH CONTACT UNDER THE INFLUENCE OF SAID ABNORMAL TEMPERATURE RISE AND RETURNING TO ITS ORIGINAL POSITION WHEN THE TEMPERATURE RISE NO LONGER EXISTS; ELECTRICAL CONDUCTOR MEANS CONNECTING SAID FOURTH CONTACT TO SAID ONE SIDE OF THE STARTING CIRCUIT; WHEREBY WHEN SAID THIRD AND FOURTH CONTACTS ARE IN ELECTRICAL CONNECTION SAID SWITCH IS JUMPED PERMITTING THE CONTINUED FLOW OF CURRENT THROUGH SAID TEMPERATURE RESPONSIVE MEANS, THUS HOLDING SAID SWITCH OPEN AND PREVENTING THE CONTINUED REPEATED OPERATION OF THE STARTER. 